It has long been known in the art to provide holding tanks for toilet and other waste systems utilized in common carriers, such as airplanes, trains, busses and the like. Generally these systems all include a holding tank which contains both the solid and liquid waste materials. In each of these systems, it is necessary to provide a means by which the waste holding tank may be emptied or drained.
In the past, in particular in connection with aircraft toilet systems, the waste drain valve assemblies employed almost exclusively utilized a ball valve equipped with one or more elastomer seals. The ball valves were typically spherical units having a cylindrical passageway running through the unit. In the open position the cylindrical passageway was aligned with the waste holding tank and the exterior outlet drain. In the closed position the ball valve was rotated 90.degree. such that the valve body blocked both the holding tank and the outlet drain. In these prior devices the seals were maintained in constant contact with the body of the ball valve itself. When the ball valve was rotated from an open to a closed position and/or vice versa, the seals remained in contact with and scraped over the surface of the ball valve resulting in a flexing of the elastomer seals through friction with the surface of the ball valve which led to premature deterioration of the seals and ultimately leakage through the seal. Additionally, waste material which adhered to the surface of the ball valve body was forced into contact with the seals whereby the seals were used as a scraper to clean the waste matter off of the ball valve. This also led to damaged seals or enhanced and expedited the deterioration of the seal with the ultimate problem of leakage around the ball valve occuring. In order to prevent or minimize the risk of leakage, the prior designs frequently utilized multiple seals with one seal being located at the top or waste tank side of the ball valve and the second seal being located at the bottom or drain outlet side of the ball valve. However, experience has shown that these prior valves prematurely developed leaks due to the constant contact and friction between the ball valve and the seals which resulted in the seals being damaged through normal use with the resulting leakage occurring.
In addition to being unsanitary, the leakage which occured in the prior designs resulted in the undesirable formation of ice on the exterior of the airplane during flight which created an unacceptable hazard for people and objects on the ground. In the event of a faulty or leaking valve assembly, it is not uncommon for large blocks of ice, weighing several pounds, to be formed from the leaking waste water which on occasion break free from the airplane creating a hazard to flight safety and those on the ground.
A need therefore exists for a valve mechanism that may be utilized in toilet or other waste systems which satisfactorily prevents leakage from the system.
A need also exists for a waste valve assembly for airplane toilet systems which avoids premature wear or damage to the seals. It is an object of the present invention to provide a low cost, light weight, efficient valve assembly for use in airline toilet systems which properly seals the drain tank and prevents premature damage or wear to the seals.